Search

High-energy continuous wave (CW) laser ablation can cause severe damage to structural materials in an extremely short time, which generates considerable concern in terms of material safety. For the purpose of reducing or even eliminating such laser-induced damage, a novel composite coating consisting of a boron-modified phenolic formaldehyde resin incorporating ZrC and SiC has been designed and prepared. The experimental results reveal that ZrC and SiC are rapidly oxidized to ZrO 2 and SiO 2 respectively, leading to the formation of a white ceramic layer consisting of ZrO 2 particles and melted SiO 2. After ablation at 1000 W/cm2 for 50 s, elemental analysis indicates that no Si can be found in the central ablation zone because of gasification. A relatively compact ZrO 2 layer is formed through the sintering of adjacent ZrO 2 particles, which effectively improves the reflectivity of the coating from 7.3% (before ablation) to 63.5% (after ablation). The high reflectivity greatly reduces the absorption of laser energy. In addition, no obvious ablation defects are observed in the composite coating. The excellent anti-laser ablation performance of the coating makes it a promising system for protecting a material against the effects of long-term CW laser ablation. [ABSTRACT FROM AUTHOR]

Abstract Laser is becoming increasing threat to materials due to its high energy that can induce thermal damage, especially high energy continuous-wave (CW) laser. In this case, laser protection has attracted more and more concerns. Nanocomposite coatings that consist of nano-copper filler with phenolic resin matrix have been designed and successfully prepared to meet the requirement of anti-laser ablation. The anti-laser ablation ability of the nanocomposite coatings is evaluated through the temperature of the back-surface substrate. Results show that the transpiration cooling effect of nano-copper particles do improve the anti-laser ablation property of the coating. The residual char with porous structure which is the pyrolysis result of phenolic resin plays a key role as a barrier to prevent laser from irradiating inside of the coating. The amorphous carbon gradually transforms to graphitic structure during CW laser irradiation. The latter has better stability at high temperature, improving anti-laser ablation. The micro-morphologies and element content analysis indicate that the evaporation of nano-copper particles occurs layer by layer until the total pyrolysis of phenolic resin located in the vertical direction of the coating. All the analyses show that this nanocomposite coating has excellent performance as a protective shield to anti-laser damage. [ABSTRACT FROM AUTHOR]

High-energy continuous-wave (CW) laser has been considered as a significant technology in recent decades. Such laser can destroy conventional materials in an extremely short time, necessitating their protection. In this study, zirconium carbide (ZrC) and silicon carbide (SiC) particle-modified short silicon carbide fiber-reinforced phenolic resin matrix composites (SiC/BPF-ZS) with significant anti-laser performance were designed and prepared. Our results showed that the ceramic particles and SiC fibers rapidly oxidized, leading to the formation of a ceramic coating composed of ZrO 2 and SiO 2. Owing to the formation of the ceramic coating, the reflectivity of the composites improved significantly from 15.8% to 73.2% after ablation at 500 W/cm2 for 30 s. Additionally, the SiC fibers played an important role in the formation of a high-reflectivity coating during laser ablation. Contrast experiments indicated that SiC fibers lead to better performance than the carbon fibers. The high reflectivity and low mass ablation rate are demonstrated to be the key factors improving the anti-laser ablation performance of the SiC/BPF-ZS composites. [ABSTRACT FROM AUTHOR]

Despite many years of use of boron-modified phenolic resin (BPF) in the aerospace and auto industry, it is still unknown if such resin can be used in extreme environments, especially under exposure to high energy continuous-wave (CW) laser that can totally destroy many traditional materials in several seconds. Compression molded BPF plates are tested with high energy CW laser to study the laser ablation behavior. Results reveal that the laser parameters including irradiation time and laser power density have a great effect on the ablation morphology and mass ablation rate. BPF keeps decomposing into residual char due to the high temperature caused by laser. The graphite structure of residual char is gradually improved during laser irradiation, resulting in improved thermal stability of residual char. In addition, the micro-morphologies reveal that the residual char possess porous structure which leads to the thermal insulation property and minimizes the ablation damage propagating into the BPF bulk. Both the improved thermal stability and the thermal insulation property of the residual char can mitigate the ablation damage caused by the high energy CW laser. Unlabelled Image • Laser ablation behavior of boron-modified phenolic resin was first proposed. • The degree of graphitization of the formed residual char was demonstrated to keep increasing during laser ablation. • The porous structure of residual char is proved to be the key factor leading to the thermal insulation property. • The reason why boron-modified phenolic resin owns excellent laser ablation resistance is clearly proposed. [ABSTRACT FROM AUTHOR]